It is based on a large mass of unpublished material, and considerably modifies, e.g.
The most important feature of this vowel is the rounding of the lips in its production, which, according to its degree, modifies the nature of the vowel considerably, as can be observed in the pronunciation of the increasingly rounded series saw, no, who.
As a writer, too, Gregory modifies Augustinian beliefs into forms which make them more available for Church teaching - a process very characteristic of Western Catholicism and carried still further in later centuries (notably by Peter Lombard).
Again Ritschl modifies the doctrine of sin.
Where he finds things which would obviously clash with the customs of his own day, he unhesitatingly modifies them.